Temperature of lathe headstock

[DennisWA]

My Colchester Student lathe’s headstock never gets hot to the touch when working.

By comparison a friend’s Myford Super 7 headstock gets hot to the touch (I measured it as 80 to 90 deg F). Is that too hot?

Thanks for any comments
Dennis

 

[Bob Korves]

The shop manual for the lathe should tell you the correct answer. Typically, if you can keep precision bearings, running with preload and solidly mounted, under 100F or so, they will work fine. At some point, the temperature increase causes a significant size increase, and the increased preload then increases the temp., and then it feeds on itself and finally the bearings fail. When running in a new machine or after a rebuild or bearing adjustment, it is wise to keep checking for runaway bearing temps.

 

[DennisWA]

The shop manual for the lathe should tell you the correct answer. Typically, if you can keep precision bearings, running with preload and solidly mounted, under 100F or so, they will work fine. At some point, the temperature increase causes a significant size increase, and the increased preload then increases the temp., and then it feeds on itself and finally the bearings fail. When running in a new machine or after a rebuild or bearing adjustment, it is wise to keep checking for runaway bearing temps.

 

[george wilson]

I had a 19" swing Romanian made Promaster at work. Its head would reach 180 º The headstock would swell up .002" ! More things wrong with that lathe than you could shake a stick at! Luckily I was in a museum,and not using the lathe all day in a production setting. It was also so LOUD I got really tired just listening to it.

 

[DennisWA]

Hi George
Is this a wrong post? This thread covers headstock temperatures.
Cheers
Dennis

 

[mksj]

The Promaster is a lathe, the discussion is on headstock temperature, George addresses the issue of headstock temperature and its affect on dimensional changes. In a lathe I would assume that there is some issue if you are seeing a headstock temperature reaching up to 90C (194F) and the lathe is not destined to last too much longer. There are many factors that can affect heat generation, so kind of apple to oranges with respect to comparing a Myford 7 to a standard gearhead splash lubrication lathe headstock. My understanding is that the Myford Super 7 has no speed gearbox other than a belt drive, but does use a dry clutch system. If the clutch was not adjusted properly, there was a bearing preload issue or improper bearing lubrication, these could result in excessive heat generation. As George indicated this dramatically changes the operating tolerance and can lead to a runaway thermal failure. The short answer, at 90C it is running too hot.

The ideal equilibrium operating temperature varies I have seen something like 95 to 115 degrees F which seems a bit conservative. Maximum temperatures should not exceed 170 degrees F. Timken's published specs for tapered roller bearings, including bearing life specs, assume an operating temperature of 130 degrees F. The other major factor in a oil bath gearhead lathe is the type of oil used, also that non-pressure lubrication systems (lathes) usually rely on splash lubrication. Too high of a viscosity oil, improper lubrication properties and possibly excessive foaming may all lead to poor bearing lubrication/failure and excessive friction from the gears in the oil bath. These all lead to excessive heat production, and can result in premature mechanical failure. Often manufacture give specific break in procedures for lathes/mills, these usually have to do with the bearings and to a lesser degree gears, so both seating issue and preventing excessive temperatures from the initial tight tolerances. Failure to follow these procedures can result in excessive bearing heat which will cause premature failure.

 

[Ulma Doctor]

My Colchester Student lathe’s headstock never gets hot to the touch when working.
By comparison a friend’s Myford Super 7 headstock gets hot to the touch (I measured it as 80 to 90 deg F). Is that too hot?
Thanks for any comments
Dennis

Hi Dennis,
the rule of thumb i learned is,
if you can't put your hand on the headstock for more than a couple seconds, it is running too hot.

@mksj brings up excellent points

 

[Brnoczech]

I have a Myford Super 7 that I have posted pictures of elsewhere on this site. It has 8 basic speeds, a high/low pulley on the motor and 4 different pulley sizes on the spindle and the countershaft. The countershaft rides in oilite bearings that are fed from two oil cups. Excess oil bleeds from the left bearing down into a ball thrust bearing that is engaged whenever the clutch is disengaged. I never get any excess heat from the countershaft area. The spindle rides in two ball bearings on the left side that are fed from a gits oil nipple. The spindle on the right side is cone shaped and is supported in a cone shaped bronze bearing that is lubricated by an oil wick fed from an oil cup. I have replaced the oilite bearings and the two spindle ball bearings, and followed the Myford instructions for adjustment of the ball bearing preloads and also for the adjustment of the spindle within the cone shaped bronze bearing. Although I have never measured the temperature, I can say that the oilite and ball bearings do not generate much heat, but the headstock over the right cone end of the spindle and the bronze cone bearing can become quite warm. Obviously the adjustment of the spindle back and forth, and the clearance at the spindle cone/bearing, will have a significant impact on the heat generated. Too much clearance and you risk spindle axial movement, too little and you generate more heat. Since I am a hobby machinist, and don't run the lathe constantly for hours at a time, the heat generated is manageable. Properly adjusted, the spindle moves freely, even with some heat buildup/expansion. I don't know what other lathes have similar cone shaped bearings on the inboard in, or what their lubrication methods might be, but some heat is probably inherent in that design.